For more examples, click here, but be advised that a LOT of the videos tagged as automatic strikes are just ~8 seconds of random broadcast footage with no actual game action.

Pitch Timer Violation

With no one on base, before each pitch, the pitch timer will count down from 15 seconds. Both the pitcher and the batter are responsible for being ready to go before the timer runs out. There are timers placed in various spots around the field, so that both the pitcher, batter, and umpire can see how much time is left, so no one has any excuses about being tardy.

The batter must be in the batter's box and ready for the pitch before the pitch timer reaches 8 seconds remaining. This doesn't necessarily mean that they are stone still, as most batters have a lot of pre-pitch swinging and wriggling that they will do as they wait for the pitcher. However, they need to be "alert to the pitcher," which generally means paying attention to said pitcher, before the timer ticks below eight seconds. If they can't do it, the umpire can award an automatic strike.

The pitcher, meanwhile, must have started their pitching motion before the timer runs out. This doesn't mean the ball has to be released before time runs out, just that the pitcher must have at least started their windup. If they haven't, the umpire can award an automatic ball.

Pitch timer violations tend to be a little more subtle than you might want them to be when you're watching a game. Ideally, the umpire will step out from behind the plate to indicate that something's up, and they may make an additional gesture, pointing to an imaginary watch, then pointing to whomever of the pitcher and batter have violated the timer. If you're in the stands, you might not even notice unless you're really focused in. If you're watching on TV, you'll have a slightly better chance, especially if one of the announcers picks up on what's happening, though that's not entirely guaranteed.